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To survive, every multicelluar organism needs a way for cells in one part of the organism to ‘know’ what cells in another part of the organism are doing. If you think about the human body as a population, with each cell an individual person, the endocrine and nervous systems

Signalling molecules are chemical compounds that receive and transmit messages around an organism. These can include simple ‘neurotransmitters’ of the nervous system, or larger hormones (protein compounds) of the endocrine system.

• Neurotransmitters and their mode of action on Slideshare
• An Introduction to the neurotransmitter system on Slideshare
• Neurotransmitters on Slideshare

1. What is a neurotransmitters?
2. What four criteria must be met to be classified as a neurotransmitter?
3. What are the four steps in neurotransmission?
4. There are two main types of neurotransmitters – Large peptides and smaller amino acids and amines. Draw up a table showing examples of each and briefly describe how they function. For example, dopamine influences the mood and behaviour.